Vehicle braking device

Abstract

A vehicle braking device performs a following control which makes an actual value of a physical quantity follow a first target value when the actual value of the physical quantity is a value outside a dead zone and a suppression control which suppresses a change of the actual value when the actual value is a value within the dead zone in order to control the physical quantity associated with the braking force to be the first target value. The vehicle braking device comprises a setting portion which sets a second target value which follows the first target value and which is smaller than the first target value, when the first target value is increasing and a control portion which performs a control to make the actual value approximate the second target value.

The invention claimed is: 
     
       1. A vehicle braking device which performs a following control which makes an actual value of a physical quantity which is associated with a braking force to be applied to a vehicle wheel follow a first target value which is a target value of the physical quantity when the actual value of the physical quantity is a value outside a dead zone and a suppression control which suppresses a change of the actual value of the physical quantity when the actual value of the physical quantity is a value within the dead zone in order to control the physical quantity associated with the braking force to be the first target value which is the target value of the physical quantity, assuming that the dead zone is defined to be a value between a first threshold value which is smaller than the first target value and a second threshold value which is greater than the first target value, the vehicle braking device comprising a processor configured to:
 set a second target value which follows the first target value and which is smaller than the first target value, when the first target value is increasing; and 
 perform a control to make the actual value of the physical quantity approach the second target value. 
 
     
     
       2. The vehicle braking device according to  claim 1 , wherein:
 the processor sets the second target value which follows the first target value and which is larger than the first target value, when the first target value is decreasing. 
 
     
     
       3. The vehicle braking device according to  claim 1 , wherein: the processor sets the second target value to a value outside the dead zone. 
     
     
       4. The vehicle braking device according to  claim 1 , wherein: the processor derives the second target value from at least one of a magnitude and an inclination of the first target value. 
     
     
       5. The vehicle braking device according to  claim 1 , wherein: the processor makes the second target value gradually approach the first target value when a change width of the first target value is a constant state within a predetermined value. 
     
     
       6. The vehicle braking device according to  claim 1 , wherein the processor sets the second target value to a value obtained by executing a primary retarding filtering process to the first target value. 
     
     
       7. The vehicle braking device according to  claim 1 , wherein
 the physical quantity corresponds to a hydraulic pressure in a hydraulic pressure chamber; and the vehicle braking device includes: 
 a pressure increasing electromagnetic valve disposed between the hydraulic pressure chamber and a high pressure source which has a high pressure therein for adjusting a flow-rate of a brake fluid from the high pressure source to the hydraulic pressure chamber; and 
 a pressure decreasing electromagnetic valve disposed between the hydraulic pressure chamber and a low pressure source which has a low pressure therein lower than the high pressure of the high pressure source for adjusting a flow-rate of the brake fluid from the hydraulic pressure chamber to the low pressure source, and wherein the processor closes the pressure increasing electromagnetic valve and the pressure decreasing electromagnetic valve, when an actual hydraulic pressure which is an actual value of the hydraulic pressure in the hydraulic pressure chamber is a value within the dead zone.